1. Field of the Invention
The present invention relates to wastewater treatment. More particularly, the present invention relates to systems for treating wastewater including in septic tanks. Still more particularly, the present invention relates to wastewater treatment systems including airlift tubes.
2. Description of the Prior Art
Septic tanks and other sorts of wastewater treatment units are used to reduced the solids content of liquids prior to delivery to a fluid absorption field such as a leach bed. Some septic tanks are fairly stagnant in that incoming streams of solid and liquid waste are allowed to dwell in the tank until solids are separated from the liquid. The septic tank is configured so that the remaining effluent is allowed to flow to the absorption field, either directly or through a filter. Septic tanks with filtered outlets should be particularly effective at solids breakdown or removal to avoid filter clogging. Other types of septic tanks include active means for breaking down solids in the fluid prior to transfer to the absorption field. The present invention is directed to active septic tank systems.
Some active septic systems include the introduction of anaerobic bacteria to break down waste, a process which causes large particles of waste and sludge to remain within the septic tank or at least facilitates the transfer of solids to the absorption field. Other types of active septic systems force air into the tank to produce turbulence in the tank and to provide oxygen to aerobic bacteria. The aerobic bacteria sustained by air introduced into the tank interact with solids in the fluid and break them down but do so more quickly than in the systems that use anaerobic bacteria. Existing septic systems provide an anchor of sorts in the form of a bacteria retention medium to retain bacteria within the tank. These media have some porosity to enable bacteria growth therein and thereon. Septic systems including such media are referred to as fixed film systems. However, the growth media can become clogged over time whether by bacteria growth or other solids in the fluid, such as hair, for example, thereby reducing treatment efficiency and increasing maintenance requirements. It is desirable to provide the effectiveness of aerobic bacteria treatment without the limitations associated with the use of fixed film arrangements. Suspended growth systems provide oxygen for unanchored bacteria to grow.
Existing septic systems that include air introduction systems such as airlift arrangements include an airlift tube of fixed height. As a result, they are limited in their usage to septic tanks having a capacity of no more than 1500 gallons. Attempts to adjust the positioning of the tube in a larger tank include the addition of spacers under the tube. That haphazard fix in the turbulent environment of the tank can cause the tube to fall over and become substantially ineffective. It is desirable to have a system for treating wastewater in a septic tank or other containment tank that is configured to be functional for any container size.
Another limitation of existing systems is that they require the use of ballasting to keep them in a fixed position within the tank. It is desirable to have an airlift configuration that does not require ballasting so that it may be placed in a desirable location and moved, if desired, within the container. It would also be useful to be able to locate the airlift tube anywhere in the tank, including above the floor of the tank. Further, the effectiveness of the aerobic bacteria and the general performance of the septic tank are optimal when the pH in the tank is close to neutral. Unfortunately, there is a tendency for the fluid and contents entering the tank to be acidic. If that acidity is too much, the bacteria can be harmed and thereby rendered ineffective. It is desirable to ensure that the fluid in the tank remains close to neutral pH.